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Cut and drill versus nesting

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Operations Excellence by Sepp Gmeiner
Sepp Gmeiner is a partner with Lignum Consulting. For feedback, questions and/or suggestions please email s.gmeiner@lignum-consulting.com
I frequently get asked about how to decide between a panel saw or a nesting router. Nesting is well established, especially in the kitchen manufacturing sector, much more so in North America than in Europe.
There is no absolute rule as to which is better or more productive. There is no one-size-fits-all solution. In this article I would like to outline many of the factors to help guide you to a fact-based decision.
If we compare the production rates in a typical kitchen cabinet manufacturing 
scenario, we can safely assume the following production rates: The panel saw can, depending on the make and model, cut 4 -6+ sheets at the same time versus a nesting router which processes only one sheet at a time. Depending on make, model, operator and cutting pattern, the saw can process 55 – 80 books per 8-hour shift.
Nesting routers, also depending on make, model, configuration and cutting pattern, can produce 70 -100 sheets per eight-hour shift. So, on a 1-sheet comparison, the processing speed is faster on a nesting machine. Additionally, the surface drilling is done at the same time at no additional cost.
The processing rate changes drastically if you can cut two or more sheets at the same time. Therefore, the key number I usually like to establish is the average book height at the panel saw. The book height is the number of sheets with the same cutting pattern.
If the book height (average sheets/cutting pattern) is below 2, or even below 1.5, then nesting is probably the better way to go. I have seen averages below 1.2 sheets/pattern. There are two key factors that impact this book height.
One factor is the level of standardization. This is how much the company can control the different raw materials (thickness, board size, colour selection…), product variety (dimensions, roster, custom-sizes…)
The other factor is batching (related to scheduling and the manufacturing model). The more you batch, the more you can increase the book-height.
I am usually not one to advocate increasing batch sizes! In most of my work I am pushing and arguing against increased batching, as it goes against Lean principals and usually has disadvantages, such as less flexibility, higher space requirements, and longer factory through-put time.
The graph below depicts the nesting vs. cut &drill advantages, depending on production volume and level of standardization.
Smaller operations, producing less than 80-100 cabinets /day are usually better off with nesting technology. The volume can be processed by one nesting machine. (1 sheet equals approx. 1 cabinet).
Below that threshold, the level of standardization will not play a huge factor.
As the volume per day increases, the level of standardization starts to play an increased role. At the extreme, the most standardized kitchen cabinet line is probably IKEA, and it is produced in daily quantities which are off the chart. It’s obvious, the combination of high volume and high standardization clearly makes the cut and drill option win hands-down.
If you are a manufacturer of highly customized kitchens (material, sizes, features and options…) then no matter how high your daily volume reaches, you are forced by practicality to produce kitchen by kitchen, which is best done with nesting.
With this we establish the parameters of the four corners of the graph. However, it leaves a substantial gap in the middle. In this middle ground the difference is not as pronounced, and companies can be successful either way. When looking at the graph, there is no scaling on the level of standardization.
This scaling is not straight forward to establish and quantifying the level of standardization is rather complex.

Shift to higher product variety
Small and medium-size manufacturers are typically setting themselves up to be more flexible towards product variety, whereas, larger companies are more restrictive. This is driven more by the difficulty of managing the product variety than by customer focus. All have market pressure 
for more product variety. As you invest in new equipment, I recommend you push the envelop to more flexibility, which again, supports nesting.

One-piece flow
Nesting does not require any batching. You almost run cabinet by cabinet and get a similar material yield as if you were to run kitchen by kitchen. In combination with a storage and retrieval system this proven technology is already a good step towards one-piece flow.

Nesting comes out on top
Based on all these factors, in most cases, the nesting technology is the most suitable for kitchen cabinet manufacturing. Its speed provides productivity. The flexibility supports Lean manufacturing, and the increased dimensional accuracy allows production with narrower tolerances. As you produce in smaller batches there is less time and space required for sorting.

Nesting plant-Saw support
I would not call the saw technology outdated. As volume increases, there is a place for a panel saw.
There are a number of parts, such as drawer box parts, adjustable shelves, or thin backs which could be produced more efficiently on a saw. Also, service parts could be produced by a saw to keep these interruptions away from the main stream processes.

Hardware inserting
When inserting hardware like hinge blocks or shelf supports, the holes are not pre-drilled; they are drilled at the insertion machine. As inserting machines become more popular, saws can take over more of the production volume.

Conclusion
Nesting is, in most cases, the better solution but, as previously stated, there is no one-size-fits-all solution. If a company is at the crossroads for making a major investment decision, they should seriously look at the above factors as well as their vision and strategy for the future.

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